[log4perl-devel] Appender::File : File handle gets undef

[Ronald F. <yn...@mm...>]

We recently found that once in a while (every couple of hours), File.pm
crashes on a write operation. 
By inserting a suitable check, we found that the file handle happens to
be undef in File::Appender::log().

The logger in question is a bit unusual in that it undergoes frequent
file switches - frequent means that 
on times there might be even serveral  file switches per second.

The appender is defined by passing a reference to a string to
Log::Log4perl::init(), like this:

init(\ qq(
...
      log4perl.appender.Reqlog=Log::Log4perl::Appender::File
      log4perl.appender.Reqlog.name=$requestlogger_appender_name
      log4perl.appender.Reqlog.filename=$initial_reqlog
      log4perl.appender.Reqlog.mode=append
      log4perl.appender.Reqlog.layout=Log::Log4perl::Layout::PatternLayout
      log4perl.appender.Reqlog.layout.ConversionPattern=%.5p
      %d{HH:mm:ss} %M(%L) %m%n
...
));

The variables interpolated into this string are defined as follows:

use File::Spec::Functions qw(devnull);
my $initial_reqlog=devnull; # NUL on Windows
my $requestlogger_appender_name='ReqlogApp';

The "file switching" is done using the following code:

Log::Log4perl->appender_by_name($requestlogger_appender_name)->file_switch($relpathname);

During the lifetime of the program (which runs uninterrupted for days,
sometimes a few weeks), maybe 
30-100 files per day are created that way, but the number of file
switches is considerably higher,
because sometimes only one or two lines (or even none!) are logged into
one log file, then a switch to 
another logfile occurs, then a switch back to the first one, etc.  I
mention this, because it might be 
possible that our problems are related to the file switch pattern. 

At the moment we have no idea why the file handle suddenly would be
undef, and we try to research
further. At the moment, it would already help if someone could point out
whether

- the problem of "disappearing file handle" has already bee seen before,
or
- have a better guess what could be the cause of our problem (maybe
Windows gets upset
due to so many "opening and closing of files"?)

Ronald




-- 
Ronald Fischer <ro...@em...>
+  If a packet hits a pocket on a socket on a port, 
+  and the bus is interrupted and the interrupt's not caught,
+  then the socket packet pocket has an error to report.
+		(cited after Peter van der Linden)